The present invention relates to a three dimensional imaging device, that is to say a device for obtaining three dimensional data of a target surface, whether such data is displayed in three dimensional form or not. Indeed, the data may never be displayed as such, but may merely be used to control other equipment. Such an imaging device is useful for supplying three dimensional data to other instruments. For example, such data is valuable in the science of robotics, where objects are required to be identified on the basis of their three dimensional shape, and to be manipulated accordingly. Such data is also useful in monitoring the accuracy of the shape of a series of articles intended to be identical with each other.
An objective of the present invention is to provide a three dimensional imaging device that is inexpensive to manufacture, high speed in operation, compact, and robust, and hence especially well adapted for use in robotics, e.g. for mounting on the end of a robot arm, although the utility of the present invention is by no means limited to robotics. An ordinary two dimensional television camera provides an output signal having an amplitude that is not geometrically related to the object but represents the surface reflectance properties of the object, combined with the ambient light conditions, the orientation of the object and the intensity and spectral characteristics of the ambient light. The result thus will often depend on the orientation of the object and the proximity of other objects. Primary for these reasons, the extraction of three dimensional features from a two dimensional image is often difficult to realize.
Among the various techniques suggested in the past for obtaining three dimensional data is the use of an active triangulation system employing a beam of radiation, e.g. laser light, that is projected onto an area of the target surface to be examined, combined with a position sensitive detector for measuring deviations in the reflective beam. Such a system is disclosed in my U.S. patent application Ser. No. 509,373 filed June 30, 1983 (Canadian Ser. No. 455,847 filed June 5, 1984) entitled Three Dimensional Imaging Method and Device, and in the prior documents referred to in such application.
The system described in my said prior application requires synchronously scanning of the target area under examination by a light source and a uni-dimensional position sensitive light detector. The detector detects the beam reflected by the surface area. The scanning position indicates the X and Y coordinates in a reference plane of each area, while the position in the detector at which the beam is received represents a measure of the deviation of the target area in the direction perpendicular to the reference plane, i.e. the Z coordinate. This technique has many practical uses, but requires maintenance of the object in a fixed position or under controlled motion.